The 32 oz Nalgene is good for taking to your liberal arts college class and decorating with stickers but for adventuring, the 40 oz canteen is essential to stay hydrated. The metal bottle holds no taste and washes easily. Rock the Klean Kanteen!
I use the Klean Kanteen 40 oz. everyday. I was previously using a Nalgene but with the BPA concerns couple years ago, I switched to stainless steel. First of all, the bottle hold A LOT of water. At 40oz, it's more than the Nalgene bottles at 32oz. This makes for a lot less trips to the water cooler if you're somebody like me who drinks water all day long. The loop cap is super tight and durable. I've never had a problem with it leaking as long as the cap is screwed on tight. The bottle is durable and shines up well sending it through the dish washer. The bottle will dent so be careful not to drop it. All in all I love the bottle, it holds a lot, is stylish and is really easy to clean and drink out of.